Field of the Invention
This invention relates to the production of paper and in particular to the sizing of paper using as a sizing agent water soluble salt of substituted succinic acid. The invention also relates to novel compositions of matter containing paper which has been sized using sizing agents of the present invention.
Numerous materials have been used in the past for sizing paper. Sizing using salt of certain substituted succinic anhydrides or acids is disclosed in U.S. Pat. No. 3,139,373. Sizing agents of that patent are substituted with hydrocarbon radicals having from 8 to 15, especially 10-14, carbon atoms. The patent discloses that agents whose substituent hydrocarbons radicals contain less than 8 carbon atoms or more than 15 carbon atoms give unsatisfactory results. The only substituent hydrocarbon radical having more than 15 carbon atoms disclosed in the patent is the n-octadecenyl radical of n-octadecenylsuccinic anhydride. From the examples and the claims, it appears that the patent shows a preference for normal dodecenyl substitution. In the process of U.S. Pat. No. 3,139,373, the substituted alkenyl succinic acid or anhydride is saponified with an alkaline material to form a soluble salt, which is combined with aqueous paper-pulp slurry. The resulting mixture is treated with a precipitating agent such as an aluminum salt to convert the soluble salt into an insoluble form which deposits on the pulp fibers.
Paper sizing using substituted succinic anhydrides is disclosed in U.S. Pat. No. 3,102,064. Although the patent indicates that the anhydride can be used in various ways, it appears that a preferred method of use is to form a starch emulsion of the anhydride as a working system. Unfortunately such starch-anhydride systems have a short useful "life" and must be used promptly after the preparation thereof. This necessitates not only special equipment for the preparation of the emulsions but also limits the effectiveness of recirculation of white water in paper mills that use such a recirculation technique.